Eliminate thermoelectric EMF in low-ohm measurements

Elimination of thermoelectric electromagnetic fields (EMF) that causes errors in the readings while trying to measure small voltages or low impedance are discussed. A standard way to solve this problem is subsequently averaging the two readings by reversing the excitations. An increase in excitation current increases the measurement sensitivity , the two internal 200-μA excitation currents appear in parallel with each other. Port pins P1 and P2 of the AD7719 drive the transistors in antiphase mode.